correlation coefficient

A measure of the degree of interrelationship which exists between two measured quantities,
and
; the correlation coefficient() is defined by the following relation:

where
and
are the measured values in the
th experiment of
total experiments,
and
are the arithmetic means of
and
:

(similar expression for ).
The linear correlation coefficient indicates the degree to which two quantities are linearly related. If
is followed then
, and departures from this relationship decrease ; if interpretations of data based on the linear correlation coefficient are to be made, one should consult a book on statistics.